Optimal DC link voltage stabilisation technique for a grid-connected PV system

The utilisation of renewable energy (RES) powered microgrids has seen significant growth due to environmental concerns. These RES resources are often integrated with the grid through a DC link. Maintaining the DC link voltage at a specified level is of prime importance to ensure smooth and efficient supply in the presence of fluctuating RES. Therefore, this work presents a fractional order super twisting sliding mode control technique (FOSTSMC) to stabilise the voltage, reduce response time, and overshoot at the DC link of a grid-connected microgrid. The microgrid under study is composed of a photovoltaic (PV) system with an incremental conductance and integral regulator-based maximum power point tracking (IC+IR MPPT) algorithm. Firstly, a conventional proportional-integral (PI) control-based voltage control technique is implemented, which is considered a benchmark technique for comparison and validation purposes. Secondly, the proposed control technique is implemented to control the DC link voltage to a reference voltage in constant and varying solar irradiance. Additionally, an Ant colony optimisation algorithm is used to optimally tune the coefficients of the FOSTSMC controller. The simulation results demonstrated the effectiveness of the ACO-FOSTSMC which exhibits 72% lower settling time, and no overshoot when compared with the benchmark technique. The results of the PI controller exhibit a longer settling time with a 23.6% overshoot, and 26% undershoot. The results indicated that the proposed control strategy can be effective in maintaining the DC link voltage to ensure a smooth power supply.